BIO 105 – Water Cycle, Carbon Flow, Global Warming & Photosynthesis

The Water Cycle

Carbon cycles between living organisms, the atmosphere, bodies of water, and the soil.
CO_2 is absorbed by oceans, plants, etc., and converted into organic carbon (sugars) by photosynthesis.
CO_2 is released through respiration, decomposition of organic matter, and burning of organic material.
Fossil fuels are stored sources of carbon; burning them increases CO_2 release.

CO_2 is a greenhouse gas that absorbs and emits thermal radiation.
Excess greenhouse gases cause global warming.
Global warming is the progressive increase of Earth’s average temperature.
Effects include melting glaciers, rising sea levels, habitat loss, and climate change.
Deforestation contributes to global warming by reducing CO_2 absorption and releasing methane.
Major sources of carbon dioxide emissions are industry, transportation, and commercial/residential/agricultural activities.

Photosynthesis is performed by plants and some microorganisms (not animals or fungi).
Equation: CO2 + H2O + \text{light energy} \rightarrow C6H{12}O6 + O2
Photosynthesis occurs in organelles called chloroplasts, within thylakoids and stroma.
Light Reactions: Occur in the thylakoids, converting light energy into chemical energy (ATP and NADPH), and produce ऑक्सीजन (O_2).
Calvin Cycle: Occurs in the stroma, producing sugars using ATP and NADPH.
Stomata regulate gas exchange in leaves; guard cells control stomata openings.
Higher temperatures can lower the rate of photosynthesis due to transpiration (water loss).

Overall Equation: 6CO2 + 6H2O + \text{light energy} \rightarrow C6H{12}O6 + 6O2
Increased CO_2 does not necessarily lead to more photosynthesis due to increased temperature and water loss (transpiration).